The authors conducted a prospective study to compare the measurements obtained by objective alternate prism and cover test (PCT) and the subjective red glass test in 72 patients aged 60 years on average and with a mean visual acuity of 20/23. Mean angles obtained by alternate PCT were 9.1PD distance horizontal, 5.1PD distance vertical, 10PD near horizontal and 2.5 near vertical. Mean angles obtained by RGT were 10.2PD distance horizontal, 6.8PD distance vertical, 12.2PD near horizontal and 3.2 near vertical. The differences were statistically significant. The bigger difference remained too small for clinical significance with regards to surgical planning but could help with diagnostic provision.